1. Field of the Invention
The present invention relates to methods and systems for collect call service, and more particularly, in order to charge a uniform toll for collect calls regardless of location and/or type of receiver's terminal, methods and systems for establishing a call link between a caller and the receiver through a VoIP network that is free for charge and a conventional network that is charged for the receiver.
2. Description of the Related Technology
Conventional telecommunication services have been a media for only voice communication, however, current telecommunication services are evolving to new means for providing various high-quality services. The goal of present telecommunication service provider is to provide a new telephone service, which is customized to the subscriber's needs, with low cost and efficiency, and it is the most important thing to get a competitiveness than rivals. Internet, the most suitable solution that can make this goal possible, becomes an essential part of ordinary life with explosively increasing number of users. The connection between PSTN network and IP network gives various opportunities to wired service providers, mobile service providers, ISP (Internet service provider)s, device manufacturers and value-added information service providers, respectively.
The efforts to provide the conventional telephone service and value-added service through Internet, both previously provided on PSTN network, are being made by standardization bodies such as IETF, ITU, ETSI, and so on. IETF has proposed several standards such as SIP (session initiation protocol), SDP (session description protocol), MEGACO (media gateway control protocol), SIGTRAN (signaling transport) for Internet telephony and value-added service on Internet. H.323, ITU-T studied from 1990, is a standard for communicating voice/data/image between terminals on packet network. In H.323, four essential entities, which are terminal, gateway, gatekeeper and MCU (multipoint control unit), were defined for the purpose of communication on network, and H.323 v3 supporting TCP and UDP is currently published. In order to meet the needs for common solution such as VoN (voice over network), ETSI (European Telecommunications Standards Institute) established TIPHON (Telecommunications and Internet protocol Harmonization Over Networks) for development and standardization in considering technical issues occurring when SCN (Switched Circuit Network) and Internet are connected to each other. Currently, among VoIP standards, H.323 is the most widely used. FIG. 1A illustrates a schematic of VoIP network according to H.323 standard. PSTN phone 10b can set up a call directed to a receiver's phone 13 through a registered gateway 11a and VoIP stand-alone phone 10a can also set up a call directed to the receiver's phone 13 without gateway. Calling/called gateways 11a, 11b as a node for entering into a different network match networks that operate based on H.323 standard and different standards, and convert data and control signals entered from one network to be suitable for the matched network. Gatekeeper 12, one entity of the H.323-based network, binds several endpoints, for example, gateway, user terminal (PC, VoIP stand-alone phone), MCU (not shown) into a specified portion of the network called a “zone” and performs control/management/registration on them included within the zone. Gatekeeper 12 is not an essential entity in H.323-based network, however, it can perform some main tasks such as an address conversion, a call acknowledgment, and a bandwidth control, and some additional tasks such as a call control, a billing and generation of statistical data. So far, the most preferable billing method for the voice telecommunication service that has been introduced in VoIP system is a method using prepaid card. The prepaid car has exchangeable value in various forms such as cash, point, mileage, coupon and so on. Because there are so many calling parties and calling terminals on VoIP network rather than on PSTN network or mobile network and consequently it is very difficult to charge respectively for each call, the prepaid card was the most effective solution for VoIP billing system. But, although service charge of voice telecommunication service of VoIP network is cheaper than that of any other networks, the number of VoIP users does not increase because a user is forced to buy the prepaid card before using VoIP network. In another method, a user may use postpaid after contracting with a service provider before use.
Differently from the VoIP system, the number of users for collect call in PSTN network is increasing more and more. Even if the collect call service was originally provided by PSTN service providers who suffered from rapid decrease of subscribers due to the development of mobile telecommunication, currently the mobile telecommunication service providers provide the same service. FIG. 1B illustrates a telecommunication system for collect call service. The caller enters a collect call identifier and a called party's number on phone 20a, 20b and if the called party accepts the collect call, toll for the collect call is charged to the called party. For example, if the caller 20b makes a call on mobile phone to the called party 25a, PSTN subscriber, the tolls for using mobile network and PSTN network are charged to the called party. Thus, it is the problem of the conventional collect call service that toll of collect call is changed according to not only the type of called party's terminal but also the type of caller terminal.
FIG. 1C is a flowchart of the conventional counsel service based on ARS (Auto Response System). Referring to FIG. 1C, a user who wants a charged counsel (hereinafter, “counsel user”) makes a phone call to the phone number that the counsel user already knows at step 30. The charged counsel services on PSTN/mobile network are provided through ARS, and there are many kinds of systems such as fortune, stocks, tax and so on. On receiving a phone call, ARS generates several voice menus which the counsel user can select and receives the selection of counsel user at step 35. When the call is connected between the counsel user and the selected counselor at step 40, the counsel user must explain what he wants to be advised (hereinafter, “basic information”) at step 45, then listens the result of counsel (hereinafter, “counsel information”) at step 50.
Most of ARS counseling systems charge the toll only after the call is connected to the ARS counseling system. It takes almost time of charged counsel service to select counselor and explain basic information, and if the counsel user does not explain basic information properly, consequently it makes the total time of call longer. And, since the communication means in ARS counseling service is limited to only voice, a few kinds of services, e.g. such as fortune telling or interpretation of dream that can communicate basic information and counsel information with voice, are available through ARS. Also, since ARS counseling service is provided in real time, if the counselor is off duty or plural counseling requests occur at the same time, the counseling service cannot be provided. Also, since ARS counseling service requires high-cost CTI equipment, it makes difficult for the service provider to start the ARS counseling service.
As aforementioned, there are some problems that a VoIP user is required to buy a prepaid card before use and the toll of collect call is dependent on the type of caller terminal as well as the type of called party terminal.